1. Chapter 30 : Plant Diversity II: The Evolution of Seed Plants

2. I.Seed Evolution A. The three most important reproductive adaptations in plants: 1.Reduction of the gametophyte 2.The seed 3.Evolution of pollen B.Reduction of gametophyte: 1.The small female gametophyte is surrounded by the sporophyte. -protection -nutrient source

4. C.Evolution of the seed: 1.Seed: Sporophyte embryo packaged along with a food supply within a protective coat. 2.All seed plants are heterosporous: two different types of sporangia that produce two different spores. a.Megasporangia: produce megaspores which give rise to the female (egg-containing) gametophytes. b.Microsporangia: produce microspores which give rise to the male (sperm- containing) gametophytes

5. -Layers of sporophyte tissues, integuments, envelop and protect the megasporangium. -The ovule consists of integuments, megaspore, and megasporangium. -A fertilized egg develops into an embryo -The ovule develops into a seed and fruit.

6. 3.Within this seed coat, a seed may remain dormant for days, months, or even years until favorable conditions trigger germination. 4.When the seed is eventually released from the parent plant, it may be close to the parent, or be carried off by wind or animals.

7. D.Evolution of Pollen 1.Eliminated the requirement of water for fertilization. 2.The microspores, released from the microsporangium, develop into pollen, which are resistant, far-traveling, and airborne.

8. 3.Pollen can be carried away by wind or animals until pollination occurs when they land in the vicinity of an ovule. 4.Most gymnosperms and all angiosperms do not have flagellated sperm. Instead, once the pollen lands on the stigma, it grows a tube.

9. II.Gymnosperms: Cone-bearing plants A.The seeds and ovules of gymnosperms (“naked seeds”) develop on the surfaces of specialized leaves called sporophylls. MICROSPOROPHYLLS MEGASPOROPHYLLS (male) (female)

10. B.The four extant phylums of gymnosperms: 1. ginko 2. cycads 3. gnetophytes, 4. conifers Ginkgo biloba -dioecious: male and female cones found on separate trees (Gymnosperms are known as “evergreens”)

11. Cycads: Not a fern or a palm -dioecious: male and female cones found on separate trees Female cone Male cone

12. -gnetophytes: dioecious -conifers: most are monoecious

15. III.Angiosperms: Flowering plants A.Most diverse and most geographically widespread of all terrestrial plants. B.Two main classes: 1. Monocots, 2. Dicots

16. C.The Flower: The defining structure in angiosperms 1.Female: carpel 2.Male: stamen 3.Sepal: modified leaves that enclose the flower before it buds. 4.Petals: modified leaves. Brightly colored petals are found on plants that rely on animals for pollination.

19. D.Fruit: mature/ripened ovary 1.After fertilization, the wall of the ovary thickens to form the fruit (otherwise known as the pericarp). 2.Fruits protect seeds and aid in their dispersal. 3.If the flower has not been pollinated, the fruit usually does not develop, and the entire flower withers and falls away.

21. 4.Fruit types:

22. Humans do not eat always eat the fruit. In the case of a coconut and popcorn, we eat the endosperm.

23. E.Reproductive life cycle of angiosperms: 1.All angiosperms are heterosporous, producing microspores that form male gametophytes and megaspores that form female gametophytes. 2.The male gametyophytes are contained in the pollen. a. The pollen contains two sperm. 3.The ovule contains the female gametophyte, the embryo. It consists of several cells, one of which is the egg.

25. 4.Cross-fertilization: sperm and egg from two different plants Hibiscus laevis exhibit “delayed self-fertilization”

26. 5.Double-fertilization: one sperm unites with the egg to form a diploid zygote and the other fuses with two nuclei called the polar bodies. The 3n result forms the endosperm, food source for the developing embryo.

27. F.Coevolution: Angiosperms and animals have shaped one another’s evolution.

28. IV.Plants and Human Use A. More than 25% of prescription drugs are extracted from plants, and many more medicinal compounds were first discovered in plants and then synthesized artificially.